This invention relates generally to fastener driver bits and more particularly to a system for distinctively marking driver bits of a set and of a family of sets of driver bits, and to a process for coloring driver bits so that different size driver bits can be easily recognized.
Robertson fasteners (screws, bolts, and the like) have been used since around 1908. Such a fastener has a head similar to heads of standard-groove screws and Phillips-head screws, but with a square indentation for receiving an elongated square working tip of a Robertson driver. There are, for example, Robertson screwdrivers, each having a handle, a shaft, and a square working tip for engaging the square indentations of Robertson screws. Generally, there are four sizes of Robertson working tips, often designated as 0, 1, 2 and 3 size working tips, with size 0 being the smallest and size 3 being the largest. These different size working tips are typically used to drive different size screws as follows:
The larger screws have larger Robertson square indentations and the working tip sizes for driving the larger screws are correspondingly also larger.
Robertson driver bits are also available for driving Robertson fasteners with power driving machines, such as electric drills. A problem is that it is difficult to distinguish different working-tip sizes of driver bits when an entire set of driver bits is in a tool chest. Thus, one using the driver bits must expend an inordinate amount of time choosing a Robertson driver bit with a desired working-tip size.
It is therefore an object of this invention to provide a set of, and a family of sets of, Robertson driver bits which allow a user to easily distinguish the working-tip sizes of the individual driver bits. Similarly, it is an object of this invention to provide a method of marking Robertson driver bits so that their sizes can be easily recognized.
Robertson screwdrivers are sometimes sold in sets and sometimes plastic handles of the individual screwdrivers of the sets have different colors, with the 0 working-tip size being designated by a yellow plastic handle, the 1 working-tip size being designated by a green handle, the 2 working-tip size being designated by red, and the 3 working-tip size being designated by black. This system of color coding has been found to be useful for distinguishing the different working-tip sizes of Robertson screwdrivers. However, the problem of distinguishing Robertson driver bits has remained.
U.S. Pat. No. 4,559,936 to Hill, U.S. Pat. No. 5,498,158 to Wong, U.S. Pat. No. 4,982,627 to Johnson, and U.S. Pat. No. 5,897,762 to Liu all describe color-coded power cutting tools. However, none of these systems is related to driver bits, much less to Robertson driver bits, and some of them are overly complicated and difficult to use.
According to principles of this invention, a set of driver bits for Robertson screw fasteners includes driver bits whose shaft bodies have distinctive markings thereon corresponding to respective sizes of working tips of the driver bits. These distinctive markings are consistent throughout a family of such sets. In one embodiment, the distinctive markings are different colors, each color corresponding to a working-tip size. The colors are applied to entire outer surfaces of shaft bodies of some of the driver bits by plating the shaft bodies with zinc layers and then dying the zinc layers with color dyes. Some of the driver bits are colored by applying a colored zinc coat or black oxide. This coloring is carried out before the shaft bodies are connected to their respective working tips. Once the outer surfaces of the shaft bodies are thusly colored, the respective elongated working tips are swaged to the shaft bodies to thereby form color-coded Robertson driver bits. In another embodiment, the distinctive markings are surface-irregularity rings extending about the elongated shafts, with the least number of rings corresponding to the smallest size working tip and the most rings corresponding to the largest size working tip.